Incoming: 250,000 More Beta Invites - Wave 4
Blizzard is still working hard to make everyone happy and sent another wave of 250,000 Beta Invites, bringing the total to 550,000 Annual Pass Invites since the initial wave of beta testing!

Originally Posted by Blizzard
(Blue Tracker / Official Forums)

That’s right -- we’re in the process of sending 250,000 additional beta-test invites to Annual Pass holders. Keep an eye on your email and Battle.net account for an invitation to come test Mists of Pandaria with us.

As with previous waves, it’s going to take a while for the invites to process, so we recommend checking your games list in Battle.net Account Management to see whether yours has arrived yet. Once it does, you’ll see the Mists of Pandaria beta client available for download from there. We expect this entire wave to take a day or so to complete.

We appreciate the enthusiasm of everyone who signed up for the World of Warcraft Annual Pass, and we’re working hard to get you into the beta. We know you’re excited to explore Pandaria and test the new content, and we’ll keep you posted here in the forums when we’re ready to send out another wave.